Tropical Depression Nineteen Forms Off Florida Coast

Tropical Depression Nineteen has formed off the southeastern Florida coast after producing scattered showers and thunderstorms across the Bahamas. This depression could become a tropical storm tonight or later this weekend as it moves across the state of Florida.

This is the nineteenth tropical cyclone of the 2020 Atlantic Hurricane Season. This depression is forecast to become a tropical storm on Saturday. If this system is named, it will be called Sally and become the earliest 18th named storm in Atlantic history. The current record is Stan, which formed on October 2nd, 2005.

This tropical cyclone is not forecast to directly impact Trinidad, Tobago, or the Lesser Antilles.

List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Sally.

At 8:00 PM AST, the center of Tropical Depression Nineteen was located near latitude 25.4 North, longitude 79.0 West. The depression is moving toward the west-northwest near 8 mph (13 km/h). On the forecast track, the depression is forecast to move inland over south Florida early on Saturday, move into the southeastern Gulf of Mexico late Saturday, and then move northwestward over the north-central Gulf of Mexico on Monday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. The depression could become a tropical storm before moving across South Florida overnight. Otherwise, it is expected to become a tropical storm on Sunday and gradually intensify through Monday. The estimated minimum central pressure is 1009 millibars.

Tropical Depression Nineteen Forecast Track as of 8:00 PM AST Friday 11th September 2020. (National Hurricane Center)
Tropical Depression Nineteen Forecast Track as of 8:00 PM AST Friday 11th September 2020. (National Hurricane Center)

Watches & Warnings

Tropical Depression Nineteen Watches and Warnings as of 8:00 PM AST Friday 11th September 2020. (National Hurricane Center)
Tropical Depression Nineteen Watches and Warnings as of 8:00 PM AST Friday 11th September 2020. (National Hurricane Center)

A Tropical Storm Watch is in effect for:

  • South of Jupiter Inlet to north of Ocean Reef

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, in this case within the next 6 to 12 hours.

Interests along the northern Gulf Coast should also be monitoring the progress of this system. Tropical storm or hurricane watches could be issued for a portion of that area tonight or on Saturday.

Hazards Affecting Land

Tropical Depression Nineteen probabilities for tropical-storm-force winds as of 5:00 PM AST Friday 11th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)
Tropical Depression Nineteen probabilities for tropical-storm-force winds as of 5:00 PM AST Friday 11th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

WIND: Tropical storm conditions are possible within the watch area within the next 6 to 12 hours.

Tropical Depression Nineteen rainfall forecast as of 5:00 PM AST Friday 11th September 2020. (National Hurricane Center)
Tropical Depression Nineteen rainfall forecast as of 5:00 PM AST Friday 11th September 2020. (National Hurricane Center)

RAINFALL: Tropical Depression Nineteen is expected to produce totalrainfall amounts of 1 to 3 inches with isolated maximum amounts of 5 inches across central and southern Florida, including Florida Keys. This rainfall could produce isolated flash flooding and prolong ongoing minor flooding on rivers in the Tampa Bay area.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Tropical Depression Nineteen Forecast Discussion

Tropical Depression Nineteen southeast of Florida (Weathernerds)
Tropical Depression Nineteen southeast of Florida (Weathernerds)

GOES-16 1-minute satellite data show that the system near the Bahamas that we have been monitoring for the past couple of days has quickly organized into a tropical depression. Very deep convection has formed near the center, and the 1-min data now shows enough north and northwest flow to indicate that a well-defined center is present. The initial wind speed is 30 kt in agreement with recent ship data.

It is uncertain whether the large burst of convection over the center will continue and cause the depression to become a tropical storm before reaching Florida. However, since it is only a 5 kt increase from the current intensity, it is possible that tropical storm conditions could still occur along the southeast Florida coast late tonight, and a tropical storm watch has been issued. Otherwise, after the system reaches the eastern Gulf of Mexico, steady intensification is expected through the weekend due to expected light wind shear and very warm water. Some increase in shear could occur over the northern Gulf of Mexico but that is uncertain at this time. The first forecast will stay conservative and only show a peak intensity of 60 kt in 3 to 4 days, but do not be surprised if that is revised upward on later forecasts once other models better initialize the depression.

An uncertain estimate of the initial motion is 285/7. Strong ridging over the southeastern United States is expected to steer the cyclone to the west-northwest then northwest as a mid-latitude trough erodes the western side of the ridge over the weekend. The forecast gets tricky after that because the bulk of the guidance suggests the trough isn’t deep enough to recurve the system, and instead it gets left behind, moving slowly westward early next week due to weak ridging over the southern Plains. The NHC forecast is near the corrected-consensus guidance. The uncertainty in the track forecast is much larger than normal after 48 hours, as small changes in the forecast steering flow could result in this system moving over the northern Gulf Coast faster and to the northeast of what is shown here. As a result, the risk of seeing direct impacts from this system extends well outside the cone of uncertainty, even more so than usual in this case.

Key messages for Tropical Depression Nineteen (National Hurricane Center)
Key messages for Tropical Depression Nineteen (National Hurricane Center)

Key Messages:

  1. Heavy rainfall is expected to produce isolated flash flooding over portions of central and southern Florida and prolong existing minor river flooding in the Tampa Bay area.
  2. Tropical storm conditions are possible tonight along the southeast Florida coast where a Tropical Storm Watch is in effect.
  3. The system is forecast to strengthen to near hurricane intensity by early next week as it moves across the northeastern Gulf of Mexico. Dangerous impacts from storm surge, wind, and heavy rainfall will be possible along the Gulf Coast from the Florida Panhandle to southeastern Louisiana this weekend and early next week. Residents in these areas should monitor the progress of this system and updates to the forecast, as Storm Surge, Tropical Storm or Hurricane watches could be issued later tonight and Saturday.

Forecast Discussion by Forecaster Blake from the NHC.

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